The objectives of this proposal are to better describe the fluid mechanics, physiology, and pathology of cough. Specifically, we propose: 1) to study the mechanisms of mucus transport during cough using simplified engineering models of liquid-lined airways; 2) to examine the relevance of the mechanisms described in engineering models to the lung using the steady flow dog lung model; and 3) to investigate whether repeated coughing causes structural damage to airway epithelia and/or functional alteration in the barrier properties of the trachea and bronchi. The studies will span basic engineering approaches in which all variables can be carefully controlled and described but also extend to the intact lung which is more directly relevant to cough in man. Thus the same principles and ideas can be tested at several different levels. In addition, the critical question of the side effects of cough and possible pathological changes will be investigated. The scientific team includes competence from fluid dynamics, engineering, physiology and pathology. Major resources are the experimental preparations and measurement capabilities which have already been developed. This work is of significance for two reasons: First, although cough is clearly an important respiratory defense mechanism, very little is known about how airflow is actually coupled to the movement of mucus and little is known about which factors determine the effectiveness and distribution of cough. Secondly, information should help us understand how to devise more rational strategies for inducing or suppressing cough based on a clearer understanding of the effectiveness and side effects of cough.